The present invention relates to an air filter system comprising an air filter element having an inflow face and an outflow face and comprising alternating flat and pleated layers which form alternately sealed channels, and particularly to an air filter system of the foregoing type for use with an internal combustion engine.
An essential development goal in modern internal combustion engines is to reduce emission of harmful substances. Until now, the development activities focused primarily on optimizing the exhaust emission control system. Modern exhaust emission control systems meanwhile achieve conversion rates for harmful substances greater than 97%. Increasing air pollution has led most countries to limit emissions and to continue to tighten these limits. To assure reproducibility and comparability, various test methods, ratings and limits have been developed. In the United States, for example, the limits include the category ULEV (Ultra Low Emission Vehicle) and the currently strictest category SULEV (Super Ultra Low Emission Vehicle). To filter the air used for combustion in internal combustion engines, air filter systems, particularly with filter elements for axial end face inflow, are known in the art. These filters are wound, for example, from filter layers that are alternately flat and wave-shaped. This creates channels, which are alternately sealed and thereby force the air to flow through the filter medium. As a result, the medium to be filtered enters the inlet side of the filter through channels that are open on the end face and within the filter element switches into adjoining channels that are open on the outflow face. This causes the fluid to be filtered.
Published German patent application no. DE 100 63 789 A1, for example, discloses a filter element for end face inflow, which has triangular channels that are alternately sealed such that as the fluid to be filtered flows from an inflow face to an outflow face, it must pass through the filter material. The channels are formed by alternately applying flat layers and pleated layers, such that all sides of the inflow-side channels open out into outflow-side channels.
Published international patent application no. WO 00/50149 discloses a filter element with first and second opposite flow faces. The filter medium has a pleated construction, such that the flutes are divided into an upper and a lower row of channels. The upper row of channels is sealed on the outflow end while the lower row of channels is sealed on the inflow end. However, the drawback in connection with the aforementioned SULEV/ULEV problem is that any hydrocarbons present in the intake manifold of an internal combustion engine may reach the environment when the engine or the vehicle is stopped.